the last time I rode with a friend who had just bought an expensive and hi-end 650b bike he spent the whole climb raving on-and-on about how much faster it rolled, how much better it climbed and how the 26'er was obsolete and how I was still living in the dark ages on my 26" Dixon.
He was too busy blowing the 650b trumpet on the climb up to notice that I was ahead of him and any time he took the lead and couldn't make a technical climb he was the only one to get off and push. When the climb turned to a long flowing descent full of gnar I got tired of waiting for his "faster rolling" 650b bike and left him far, far in the dust.
Drinking a couple beers on the tailgate after the ride I didn't hear him mention the merits of the 650b bike any more, only thing he mentioned was that his BB got hung up on a few rock slabs and the longer wheelbase wasn't good in the tight corners on that trail..and that I must have gotten much faster since we last went for a spin a couple months before when we were both still on 26er's :lol:
Guess there's a pro/con to just about everything but IMO as long as you're having fun on two wheels it's all good..